Make the sumac onions

• Thinly slice the red onion and place in a bowl.
• Toss with sumac, a drizzle of olive oil and a pinch of salt.
• Let sit so the onions soften and turn bright pink.

Sear the steak

• Season the steak generously with salt and black pepper.
• Sear in a hot pan with olive oil until browned on both sides.
• Add the butter and spoon it over the steak, then rest the meat.

Fry the egg

• Fry the egg in the same pan until the white is set and the yolk still runny.

Assemble

• Slice the rested steak thinly.
• Top with the sumac onions, the fried egg and sliced avocado.
• Season with a little extra sumac and serve.